A bomb that runs along the ground and up walls until it hits something or a certain time passes then blows up. Get 40 Gold Skulltula Tokens and then go to the house of the cursed rich family in Kakariko Village and one of the children will give it to you. Also can be won from the Bombchu Bowling game and some other mini-games. At night there is a bombchu shop in the back alley of the market when you are young Link (after beating Dodonogo's Cavern). Can be bought from a guy on a flying carpet in the desert. Sometimes found in chests.